Electrospinning is an important method for the production of nanofibers and functional nanofibre membranes. Because the key of electrospinning is the production of nanoflows and nanofibers, the production efficiency of a single spinneret is rather low. Currently, the electrospinning is attracting increasing interests. However, most of the related researches are fundamental and use simple devices with a single spinneret and a metal plate (or roller) as receiving electrode to produce various kinds of nanowires or nano-composite materials. Nevertheless, a promising electrospinning technique in the future must be devices with multiple spinnerets. Due to the high voltage up to thousands of volts applied on a spinneret during electrospinning, the jetted nanoflows are charged and repulse each other, which causes the unevenness of the obtained membrane. In addition, since the nanoflows repulse each other, the volume of solution jetted from one of the multiple spinnerets may be smaller than that from the single spinneret.
In order to overcome the adverse influence resulted from the interference of the nanoflows from multiple spinnerets and to increase the throughput, O. Jirsak et al from Liberec Technology University, Czechoslovakia, completely abandoned the conventional spinneret and adopted a solution supplying method of roller dipping in solution, adapting the roller in various ways to make it easy for electrospinning. The technique of O. Jirsak et al has patent applications in many counties including a Chinese application No. 200480025691.5. The corresponding device is popularly called “nano-araneid”.
The “nano-araneid” is a breakthrough and innovation of electrospinning principle. However, by analyzing the principle of the “nano-araneid”, the inventors find that problems as follows exist: discontinuousness of solution supplying results in discontinuousness and unevenness of nanofibers; and fibers transferring with help of flowing air results in weak strength, of the membrane. The later problem can not be solved easily without a follow-up cross-linking treatment. In additional, with the “nano-araneid”, the width of a membrane is determined by the width of the roller dipping in solution, and cannot be set freely without cutting.
Another effort to increase the production efficiency of electrospinning is to design an electrospinning device with multiple spinnerets. For example, when multiple spinnerets are integrated with different geometric arrangements and jet in a to-and-fro scanning manner, the production efficiency can be increased to, some extent and the evenness of the obtained membranes will be improved, see for example CN200610144191.4. However, the device involved in this invention doesn't have the capacity of continuous production and should be further developed.
“Nano-araneid” is suitable for producing a nanofiber rather than a nanofiber membrane. Other conventional electrospinning devices can be used to produce a single-layer membrane, but are not convenient for the preparation of a multilayer composite membrane.